All of the parties were hunting. Lewis was hiding in a bush, and his brother tried to warn Cook and his companions of this but it was misunderstood. A few grouses flew out of the bush, and Cook and his companions fired shots. Lewis was hit in the face, and lost an eye. Cook and his companions gave statements claiming that they could not have shot Lewis. The jury found that it was one of their shots that hit him, but they could not decide whose shot it was. The Court of Appeal ordered a new trial, which Cook appealed.
- When there are two parties, and it is proven that one of their actions caused harm, but it cannot be proven which one it was, who, if anyone, is liable?
The decision in the lower court was based upon the general Canadian rule that stated that when it is certain that one of two individuals committed the offence, but it is uncertain which one was the guilty agent, then neither of them can be convicted.
Cartwright, writing for the majority, decides not to follow this and to follow US precedent instead, from Summers v Tice and Oliver v Miles, which state that to allow both parties to escape liability is unfair because both of them were negligent. Lewis is put in an unfair position in having to prove which of the parties did it, and will not recover because of this unfair position. He agrees with this, and states that both parties must be held liable, as they were both negligent in firing their shots.
Rand concurs, but goes further to say that this burden is so unfair on Lewis that the burden must shift to the appellants to prove which one of them did it. If neither has proof then they are both equally liable, however the onus is on each appellant to prove that the other is the guilty party. This is fairer because the appellants have a better idea of what really happened than Lewis.
In the dissent, Locke says that the relationship between the two appellants is not close enough to make them share liability for each other's actions. The simple fact that they were hunting together, and were going to split the kill at the end of the day does not mean that they should be completely responsible for each other’s actions.
There is no joint tortfeasance when two parties are engaged in a lawful common enterprise, and it is proven that one of them caused harm in their actions but it cannot be proven which party actually did it, unless there are special circumstances of agency in the parties' relationship (e.g. master and servant, employer and employee, principal and agent), in which case both parties may be found liable for the resulting damages; i.e., found to be joint tortfeasors.